Debeading apparatuses are known, which are mounted to a lateral side of the base of a tire changing machine and are used to detach the beads of pre-emptively deflated beads from the edges of the rim upon which they are mounted.
Typically, a prior art debeading apparatus consists of an arm with one end hinged to a hinge that is fixed to the lateral side of the base of a tire changing machine and an opposite free end with a debeading shovel.
The arm is horizontally movable about the hinge between an inactive position away from the base and an active position, progressively moving toward the lateral side of the base.
The arm is rotated by means of a fluid-dynamic, typically pneumatic actuator, whose liner is held within the base and whose shaft projects out of the base through an opening.
The shaft has its free end articulated to a median area of the arm, to push or pull the latter.
When the arm is moved in the position away from the base, the tire repairer may place a wheel with the tire preemptively deflated, in a vertical position, between the arm and the debeading shovel.
Then, the tire repairer will operate the actuator, which will draw the arm toward the base and, as a result, the shovel will first abut the tire bead, and then push it toward the interior of the rim, to the central channel thereof, thereby detaching it from the edge of the rim against which it abuts in the inflated state and as it runs on the road.
The tire repairer repeats the debeading steps, arc after arc, until it completes the circumference of one side of the wheel, then he/she turns it and completes debeading on the opposite side in the same manner.
This prior art suffers from certain drawbacks.
A first drawback is that the force developed by the fluid-dynamic actuator cannot be adjusted and causes the arm to be quasi instantaneously pulled toward the base.
Therefore, the arm shall have a substantially abrupt debeading operation, which will result in the risk of damaging the structure of tire sidewalls with the debeading shovel, i.e. tearing the fabric that typically composes it and affecting tire safety for further use.
A second drawback is that, since the debeading shovel is articulated to the free end of the arm such that it may be displaced in space during debeading, tire repairers shall manually orient it with the utmost care, at least until it contacts the tire bead, in a first area, i.e. very proximate the rim edge, which involves the risk that the latter may be contacted thereby, and damaged.
Therefore, tire repairers shall direct the orientation of the debeading shovel only using their own forces and by quick movements, to keep pace with the action of the debeading arm.
Nevertheless, in spite of the care taken by tire repairers, the force of the actuator may exceed their physical force, whereby the debeading shovel will not be properly oriented, and hence the front edge thereof will once again impact the rim edge during debeading, with the risk of damaging it.